Method and means for bright finishing metals



Patented Aug. 14, 1934 UNITED STATESJPATVENT OFFICE METHOD AND IMEAN S FOR BRIGHT FINISH- ING METALS Arthur E. Bellls, Branford, Conn.

No Drawing. Application August 17, 1932 Serial No. 629,238

12 Claims. (01. 148- 8) In carrying out my invention, as one feature thereof, I employ an ammonium formate solution as a quenching bath for the heat-treated metal, as a hot washing liquor, or as a cold soaking bath. I have found that this solution if maintained near its boiling temperature will act very quickly to completely dissolve all scale or oxides and remove heat treatment blemishes from the surface of the" metal, while the use of the cold solution and a long soaking treatment of the metal therein, provides the metal surface with a very lustrous finish.

Also, in carrying out the invention, a metal which has its natural bright finish may be treated by the ammonium formate solution, either hot or cold, as described, and the wet solution or the residue after the volatile components of the solution have evaporated, adhering to the metal, have a greater amnity for oxygen than has the metal, so that the metal does not tarnish. Also the particular composition of this ammonium formate solution constitutes an im-.

portant feature of my invention.

With the above and other objects in view, the invention will be hereinafter more fully described in detail in a preferred embodiment thereof and subsequently defined'in the appended claims.

Inthe practical development and use of my present invention, more particularly in relation to its efficacy in the removal of scale, oxides and other surface blemishes from heat-treated metals, I have found that it is quite immaterial what the particular heat-treating medium or equipment maybe. However, best results may be obtained in the use of the present invention by bath, and preferablysuch a bath which has the characteristics of a eutectic; It is also to be understood, that my present invention may likewise be used to advantage in providing the de--.

the metal in the process of heat-treatment so heat-treatingthe metal in a highly liquid salt that when the metal is removed from such solution, it will possess an absolutely clean and bright surface of virgin metal finish. This scavenging action will take place very quickly, if the solution is maintained at a temperature near its boiling point.

When metal having a bright finish, that is, untarnished, is treated, it is subjected to either the hot or cold ammonium formate solution.

an ammonium formate solution or bath. This bath may be most conveniently and inexpensively prepared by dissolving ammonium carbonate and sodium formate in approximately equal proportions in water. Asa suitable mixture, 1' use in each one hundred pounds of water, substantially four and one-tenth pounds ammonium carbonate, (NH4)2CO3, and five and nine-tenths pounds of sodium formate, ZHQOONa. These chemical components combine to form sodium carbonate, NazCOa and ammonium formate, 2HCOONH4. The resulting solution has a slightly alkaline reaction.

The ammonium formate solution above described may be used as a quenching bath in which the metal can'be immediately immersed after heat-treatment. The use of such solution as a quenching bath for either tarnished or untarnished metal, is of particular importance in connection with heat-treating salt baths of the kind above referred to, and more especially in the production of heated treated metals having a bright surface finish. Thus by means of the present invention, a continuous process is possible in which the heated metal is passed directly and immediately from the heat treatment medium into the ammonium formate solution. A properly heat treated product having a bright or lustrousasurface finish is obtained.

Another advantageous feature of -my present 9 invention resides in the fact that after the metal is removed fromthe ammonium formate solution,.by the evaporation of the vaporizable parts of the solution and. the actiomof the solution on the metal, the wet solution or the residue after the volatile components of the solution have evaporated adheringto the metal, has a greater afiinity for oxygen than has the metal, so that the metal does not tarnish. From the foregoing description, it is believed that the particular novel features of my present disclosure and the advantages thereof in practical use or operation will be clearly and fully understood. While I have herein referred to a certain definite formula for the ammonium for- In the practice of my invention, I first form 65 mate solution and have stated the relative proportions of -its constituent components, it is, of course, understood that these stated proportions .are given for the preferred form, and that more or less variation thereof is permissible without noticeable disadvantageous effect in the results obtained in the use comprising my invention;

And the residue of essentially sodium carbonate on the bright finish metals may be modified in use as a skin or film coating. Accordingly, the privilege is reserved of resorting 0 all such legitimate changes in the details of the present disclosureas may be fairly comprehended within the spirit and scope of the appended claims.

1. A scavenging solution for removing scale, oxide and other blemishes from the surfaces of metals, said solution containing nate and ammonium formate.

2. A solution for removing scale, oxide and otherblemishes from metal surfaces comprising move the said surface blemish.

5. The. process of producing a lasting bright finish on a metal surface subject to scaling, rusting, oxidizing and tarnishing which comprises dipping such a metal surface into a solution comprising ammonium formate until the said metal surface is brightened, followed by drying the surface without removal of salt residues.

6. In the process of producing bright surfaces upon heat treated'metals having surfaces subject carbooving of scale, rust, oxides, tarto scaling, rusting, oxidizing and tarnishing, the step which comprises subjecting such a heat treated metal to the action of a solution comprising ammonium formate until said metal surface 'is brightened.

'1...In the process of producing brightsurfaces upon heat treated metals having surfaces subject to scaling, rusting, oxidizing and tarnishing, the process which comprises heat treating a metal in the usual manner in a salt bath, then quenching the heat treated metal in a solution containing ammonium formate.

8. The process of brightening the surface of a metal subject to scaling, rusting, oxidizing and tarnishing which comprises a simple dipping of the metal into a bath containing ammonium formate in solution, followed by immediate drying in such manner as to leave a surface film of residues on said metal.

9. In the production r bright finishes on metals subject to scaling, rusting, oxidizing and tar- .nishing, the process which comprises subjecting a metal surface to the action of a bath containing a-hot solution of ammonium formate.

10. In the production of bright finishes on metals having surfaces subject to scaling, rusting, oxidizing and tarnishing, the process which comprises subjecting a metal surface to the action of a bath containingasolution ofammonium I formate and sodium carbonate.

11. In the production of bright finishes on metals having surfaces subject, to scaling, rusting, oxidizing and tarnishing, the process which comprises subjecting a metal surface to the action of a-bath. containing a solution formed by dissolving in water ammonium carbonate and sodium formate.

12. In the production of bright finishes on metals having surfaces subject to scaling, rust-, ing, oxidizing and tarnishing, the process which comprises subjecting a metal surface to the action,

of a bath containing a solution formed by dissolving in 100 pounds of water, ammonium carbonate, 4.1 pounds and sodium formate 5.

P unds, approximately. a AR'I'HUR E. BELLIS. 

